High velocity pneumatic devices are used in construction work to excavate or dislodge soil from around electrical cables, gas mains, water pipes and the like. The pneumatic device has the advantage of being capable of pulverizing the soil without damaging the utility lines.
The typical high velocity pneumatic device consists of a body or housing which carries an elongated tube. The body is connected to a source of air under pressure, such as a compressor, and a valve mechanism mounted in the body controls the flow of air to the tube. Mounted on the distal end of the tube is a nozzle which is designed to increase the velocity of the air being discharged from the tube toward the soil. The typical nozzle is provided with an inwardly converging upstream end which merges into a diverging downstream end and this configuration acts to reduce the pressure of the air and increase its velocity.
High velocity pneumatic devices have also been employed to both dislodge soil or other material and to remove the dislodged soil. U.S. Pat. No. 4,991,321 describes such a device that can be used for both excavating and removing material. The device includes a body or housing which carries an elongated pressure tube and the body is connected to a source of air under pressure. A valve mechanism, located in the body, controls the flow of air to the pressure tube.
The outer or distal end of the pressure tube of the device described in the aforementioned patent is bent and projects laterally into a larger diameter removal tube. The projecting end of the pressure tube is provided with a pair of outlets, one of which faces outwardly away from the distal end of the removal tube while the other outlet faces inwardly of the removal tube. A nozzle is removably connected to the first outlet and is designed to increase the velocity of the air flowing through the nozzle toward the soil. The high velocity air being discharged from the nozzle will serve to dislodge or pulverize the soil.
The second outlet in the pressure tube of the device of the aforementioned patent contains a plurality of orifice openings and a portion of the air in the pressure tube can be directed through the second outlet to create an aspirating action to draw the pulverized or dislodged soil upwardly into the removal tube. A flexible conduit is connected to the end of the removal tube to direct the removed soil to a discharge site. Thus the device can be employed to not only dislodge the soil but to remove the soil from the excavation site.
Instead of using the device as described in U.S. Pat. No. 4,991,321 for both excavation and removal, the device can be used only for excavating or only for removal of material but in these modes of operation, it is necessary to attach a plug or closure to the outlet of the pressure tube which is not to be utilized. For example, if the device is only to be used for excavating, a solid plug must be attached to the second outlet so that the entire stream of air is directed through the first outlet toward the soil. Conversely, if it is desired only to remove material, a solid plug must be attached to the first outlet in place of the nozzle so that the entire flow of air is then directed through the second outlet to create an aspirating action. Thus, with the device of the aforementioned patent, it is necessary to remove and attach components to provide the various functions.
As the outlets of the device of the aforementioned patent are located centrally of the removal tube, the cross-sectional area of the removal tube is somewhat obstructed and if a large object, such as a stone, is drawn up into the removal tube and lodges against the projecting end of the pressure tube, the stone must be removed by shutting off the flow of air which will release the aspirating action.